This fork adds a patch to use a command-line option " -4 "
to use ipv4 addresses only from lookup-up hostnames

    https://github.com/jmullee/openntpd-portable/blob/master/patches/0014-IPv4-only-commandline-option.patch

tested on Linux (debian, alpine)

---~~~OOO~~~---

This is a new port of OpenBSD's native ntpd to other Unix flavours adding
autoconf support and the necessary compatibility layer.  It is based on
portability code from the OpenSSH and LibreSSL portable projects.

OpenNTPD has a web site at http://www.openntpd.org/

The current portable tree can be found at https://github.com/openntpd-portable

Platform Requirements
---------------------
 - adjtime(2) and settimeofday(2) syscalls or equivalent.
 - adjfreq(2) or an equivalent compatibility function for best results
 - daemon(3), setresgid(2), setresuid(2) or equivalent
 - A working arc4random(2) implementation, OpenSSL or LibreSSL
     (this project shares the same arc4random compatibility code from LibreSSL)
 - libtls (included with LibreSSL 2.1.4 or higher) is required for HTTPS time
   constraint validation.

At the time of writing the Portable version is known to build and work on:

 - OpenBSD (5.6)
 - Linux (Ubuntu 12.04, 14.04)
 - FreeBSD (9.x, 10.x)
 - NetBSD (6.1.5)
 - Solaris (10.x, 11.x)
 - Mac OS X (10.9)

OpenNTPD may work on other operating systems, newer and older, but the above
ones are tested regularly by the developer.

Reports (success or otherwise) are welcome. You may report bugs or submit pull
requests at the GitHub project: https://github.com/openntpd-portable

Thanks,
  Brent Cook <bcook at openbsd.org>.